1. Field of the Invention
The disclosures herein generally relate to an inkjet head provided in an inkjet recording apparatus used as an image forming apparatus such as a printer, a facsimile machine, a copy machine, etc, and an inkjet recording apparatus using the inkjet head.
2. Description of the Related Art
In general, as an image forming apparatus used for a printer, a facsimile machine, a copy machine, a plotter, or a combined machine of these, for example, there is an inkjet recording apparatus, with which an inkjet head is provided to discharge ink droplets to be attached to a medium, or a sheet, being conveyed, to form an image.
Here, a medium is also called a “sheet”, which is not intended to limit the material of the medium. Other terms are also used such as a material for recording, a recording medium, a transfer medium, a recording sheet. Also, an “image forming apparatus” means an apparatus configured to form an image by discharging liquid onto a medium such as paper, strings, fiber, cloth, leather, metals, plastic, glass, woods, ceramics and the like. Also, “image forming” means not only to form an image attached with meanings such as characters, figures and the like onto a medium, but to form an image without patterns or meanings onto a medium, such as just discharging droplets onto a medium. Also, “ink” is not limited to so-called ink, which can be any material discharged as liquid, for example, DNA samples, photoresist, patterning materials, resin or the like.
An inkjet head of an inkjet recording apparatus may have an actuator substrate on which multiple pairs of a pressure generating section and a pressure generating chamber are formed. The pressure generating section includes an electromechanical transducer such as a piezoelectric device. In the pressure generating chamber, which communicates with multiple nozzle holes, pressure is generated to discharge ink from the nozzle holes. The inkjet head may also have a common passage substrate on which a common passage is provided to supply ink to each of the pressure generating chambers, and a nozzle plate on which multiple nozzle holes are formed into a nozzle surface opposite to a sheet, to discharge ink in the pressure chamber. The common passage substrate, the actuator substrate and the nozzle plate are layered in order to be attached. The inkjet recording apparatus applies pressure to ink in the pressure generating chamber with the pressure generating section, to discharge ink from the nozzle holes on the nozzle plate, which forms an image on a medium.
An inkjet head described in the patent document 1, has a frame and a head cover. The frame covers the perimeter of the nozzle surface so that an opening is formed to expose the nozzle holes and the periphery. The head cover has side surfaces folded at the frame to cover the side surfaces of the inkjet head. With this structure, it is possible to protect side surfaces of the inkjet head from external forces induced when the side surfaces touch a wiper to wipe the nozzle surface of the inkjet head to remove unnecessary ink, or the side surfaces touch a sheet.
As a manufacturing method of an inkjet head, MEMS (micro-electro-mechanical systems) technology is adopted, which is a micromachining technology utilizing semiconductor processes. For example, manufacturing methods such as etching, stuttering, and the like are used to form necessary parts for an inkjet head on a silicon substrate. The parts may include a liquid chamber, a vibrating plate, a piezoelectric device, an electrode, and the like. To make an inkjet head smaller, these parts are formed smaller, and/or disposed elaborately. As a result, a greater number of inkjet heads can be made from a plate of silicon substrate (semiconductor substrate). The smaller the size is, the lower the cost.
In a conventional inkjet head, at least an actuator substrate and a nozzle plate are formed with substantially the same external dimensions. With this, the nozzle plate can be supported by the actuator substrate, which can prevent the nozzle plate from deforming when the head cover touches the wiper to push the nozzle plate.
However, if the actuator substrate is made larger to support the nozzle plate more firmly, a fewer number of parts can be taken from the same plate of silicon substrate (semiconductor substrate), which leads to a higher cost of an inkjet head.